He'll forgive and forget because he has the attention span of an autistic man.
Another straggler trying to jump in on a gang bang. You are over doing it, and you obviously don't know what Autism Spectrum Disorders are. Autism is not a medical condition, it is a broad term used for a spectrum of social disorders.
It's like someone asking what type of dog you have and you say "A dog." A dog is a broad term to cover a wide variety of dog species. The correct answer would be "Shih Tzu, Boxer, etc." or something along those lines.
The correct insult would be,"He has the attention span of a man with ADHD."